Time-resolved hydrate phase evolution and pozzolanic reactivity of OPC mixtures, considering different modifications of leached spodumene

During lithium extraction from spodumene, leached spodumene concentrate (LSC) is generated as a mineral by-product. Previous studies have indicated its promising pozzolanic potential, suggesting its suitability as a supplementary cementitious material (SCM) [1]. This study investigates the influence of the two leached spodumene (LS) modifications in LSC on the evolution of hydration phases and pozzolanic reactivity in cementitious systems. Two LSC samples with differing proportions of hexagonal leached spodumene (H-LS) and tetragonal leached spodumene (T-LS) were selected and incorporated into blended cement mixtures at 10, 20, and 30 wt.%, hydrated for 28 days. The change of mineral phases with reaction was followed by X-ray diffraction (XRD). Subsequent Rietveld analysis was performed to quantify the phases after different reaction times. Additionally, thermogravimetric analysis coupled with differential scanning calorimetry (TG-DSC) and isothermal calorimetry measurements were conducted to gain further insights into the hydration behavior and reaction kinetics. For comparison, synthetic reference phases (α-, β-, and γ-spodumene as well as H-LS and T-LS) were produced and characterized concerning their pozzolanic activity. The results reveal no significant differences in the hydration behavior of the two LSC samples, indicating that both H-LS and T-LS exhibit comparable pozzolanic reactivity. Overall, the ratio of H-LS to T-LS appears to have only a minor influence on the hydration performance and reactivity.

[1]      T. Zhang, B. Ma, H. Tan, X. Liu, P. Chen, Z. Luo, Effect of TIPA on mechanical properties and hydration properties of cement-lithium slag system, Journal of environmental management 276, 111274 (2020); doi: 10.1016/j.jenvman.2020.111274.